Acacia melanoxylon

R.Br.

Fabaceae

Classification of the genus Acacia (in the wider sense) has been subject to considerable debate. It is generally agreed that there are valid reasons for breaking it up into several distinct genera, but disagreement in the way this should be done. Some authorities have wanted to transfer this species to the genus Racosperma, but the latest decision (in 2011 and still not fully accepted) is that it remains in Acacia[

General Information

Blackwood varies considerably in height from an evergreen shrub up to a large tree with a dense, pyramidal crown; it can grow from 6 - 45 metres tall. The straight, cylindrical bole can be up to 25 metres long, though it usually branches from near the ground; it can be up to 150cm in diameter and larger boles are often buttressed[

An excellent on-line database with detailed information on over 3,200 species of useful plants of Africa.

]. The tree is often grown as an ornamental.

Known Hazards

The wood is an important cause of allergic contact dermatitis in Australia. Quinones such as acamelin and hydroxyflavans such as melacacidin are responsible for the sensitizing activity. Occupational asthma caused by blackwood has also been reported in wood workers[

An excellent on-line database with detailed information on over 3,200 species of useful plants of Africa.

].

Properties

Weed Potential

Yes

Edibility Rating

Medicinal Rating

Other Uses Rating

Habit

Evergreen Tree

Height

25.00 m

Growth Rate

Fast

Pollinators

Bees

Cultivation Status

Cultivated, Ornamental, Wild

Cultivation Details

A plant of the warm temperate to subtropical zones, able to be cultivated at higher elevations in the tropics. It shows a wide ecological adaptability in its native Australia. The mean annual temperature in its range is 6 - 19°c. Mature trees can tolerate moderate frost with occasional temperatures down to around -10°c, though young trees are more sensitive[

Excellent and very comprehensive, though it contains a number of silly mistakes. Readable yet also very detailed.

].
Blackwood has been considered one of the most important invasive plant species in southern parts of South Africa. It does not aggressively invade closed evergreen forest, but outside the forest it is a serious invader of open and disturbed sites. Seed-feeding weevils of the genus Melanterius can be used as biological control and have been imported in South Africa from Australia for this purpose. For many years a policy of eradication was followed because the tree was perceived as a threat to the indigenous forest, but recent investigations support the opinion that it is gradually replaced by native species in indigenous forest[

An excellent on-line database with detailed information on over 3,200 species of useful plants of Africa.

].
The tree is fast growing. In plantations in Rwanda during the first 12 years of growth, the increase in height was 1.5 - 2.4 metres per year and in diameter 16 - 19mm per year. In Tanzania 20 year-old planted trees were 25 - 32 metres tall, with a bole diameter of almost 50cm at breast height. Plantation trees in South Africa had a mean diameter increase of 1 - 2cm per year until the trees were 22 years old[

Excellent photos of over 1,100 species and cultivars with habits and cultivation details plus a few plant uses. Many species are too tender for outdoors in Britain though there are many that can be grown outside.

Excellent and very comprehensive, though it contains a number of silly mistakes. Readable yet also very detailed.

].
This species has a symbiotic relationship with certain soil bacteria, these bacteria form nodules on the roots and fix atmospheric nitrogen. Some of this nitrogen is utilized by the growing plant but some can also be used by other plants growing nearby[

The heartwood is golden brown to dark brown or almost black, often with a reddish tinge and dark steaks; it is distinctly demarcated from the 3 - 10cm wide, white to straw-coloured sapwood. The grain is usually straight, sometimes interlocked or wavy, giving a fiddle-back figure; the texture is fine to moderately fine; the surface is highly lustrous. The wood is hard; of medium weight; moderately durable to durable, though it is readily attacked by termites. It has good machining properties; takes a high polish; glues and stains well; steam-bending properties are good; nailing properties are poor: the wood splits easily and pre-boring is recommended. A very good quality wood with an attractive appearance, it is suitable for high-quality furniture, cabinet making and fancy veneer; and is also used for light construction, tool handles, musical instruments, bent work, turnery and fence posts.[

Comprehensive listing of species and how to grow them. Somewhat outdated, it has been replaced in 1992 by a new dictionary (see [200]).

]. The seed develops a hard seedcoat as it ripens, and may then benefit from scarification before sowing to speed up germination. This can usually be done by pouring a small amount of nearly boiling water on the seeds (being careful not to cook them!) and then soaking them for 12 - 24 hours in warm water. By this time they should have imbibed moisture and swollen - if they have not, then carefully make a nick in the seedcoat (being careful not to damage the embryo) and soak for a further 12 hours before sowing.. The seed germinates in 3 - 4 weeks at 25°c[

]. As soon as the seedlings are large enough to handle, prick them out into individual pots and grow them on in a sunny position. Plant them out when large enough.
Cuttings of half-ripe wood with a heel, planted into individual pots[